This invention is related to a new solar heater for collecting the radiant energy of the sun in a fluid. While solar heaters are old in the art, this invention relates to an economical and efficient solar heater which is relatively inexpensive and which has freezing and corrosion resistant properties.
The prior art has many forms of solar heaters, however, none has been developed which allows for efficient use of the solar heaters without the heaters being very troublesome and expensive.
Some prior art heaters using fixed plates, while being efficient, have had corrosion problems which clog the system and eventually destroy the solar heaters efficiency. Many in the prior art have attempted to resolve the corrosion problem by using corrosion inhibitors in the fluid used to collect the heat and/or by using coating on the fixed plates. The coatings, however, interfere with the most efficient transfer of heat and thus create yet another problem.
Another problem in some of the prior solar heaters which use water as the fluid vehicle for carrying the energy collected, is that the heaters must be drained during the winter nights because the water freezes and bursts the heaters. When antifreeze is added to prevent freezing and/or corrosion inhibitors are added, then the water must be passed through a heat exchanger which would transfer the heat to a separate palatable water supply to be used by humans. This step heat transfer is highly inefficient.
While the prior art has developed cheap solar heaters using flexible plastic bags, these bags are not highly efficient because they tend to expand or balloon and form relatively thick cross sections of water which are not easily heated. Also, the bags tend to allow the collection of air bubbles which reduce the heat transfer. Also, these bags cannot be tilted upward for maximum incidence with the sun because of the hydrostatic head which is created at the lowest point in the bag causing ballooning or expansion which results in a loss in efficiency. Thus the prior art has struggled with the problem of preventing ballooning while trying to get maximum water in contact with the heated surface.
Also, when flexible plastic bags of the prior art are laid upon a flat surface instead of being elevated to prevent ballooning, several other problems are created. One such problem is that the flat plastic bags are hard or difficult to drain and if the heated water is not drained then the heat is lost because it never reaches the storage tank. Yet another problem is that when the flexible plastic bag is flat the maximum incidence with the sun cannot be obtained and thus a loss of efficiency in the system occurs.
For example, U.S. Pat. No. 3,513,828 attempted one solution to obtain a solar heater for installation at an inclined surface for maximum incidence with the sun and yet prevent the ballooning effect by providing partitions which collect the water and then redistribute it thus reducing the effective hydrostatic head of the whole heater to just that from partition to partition. This heating is not highly efficient because so much of the heated surface is not in contact with the water.
Also in the prior art, when rigid panels were used so that a relatively thin sheet of water could be heated and kept in contact with the back side of the heated surface, the panels had to be very thick to have sufficient strength to keep from ballooning. With thick panels there is a very poor heat transfer and thus a loss in efficiency.
Another problem with the prior art is that of channelling in the Solar Panels, which means that water flows evenly in some places in the Solar Panel and not at all in others which thus reduces the efficiency of the Solar Heater. The prior art has tried to solve this problem by designing many narrow restricted flow ways in the Solar Heater for more even distribution but this is expensive and impractical.